JP6706481B2 - Image sensor - Google Patents

Description

The present technology relates to an image sensor. More specifically, the present invention relates to an image sensor capable of improving the saturation signal charge amount.

In a CCD (Charge-Coupled Device) image sensor, photoelectric conversion elements (photodiodes) corresponding to pixels are two-dimensionally arrayed, and the signals of each pixel that have become electric charges by the photoelectric conversion elements are vertically transferred to a CCD and horizontally transferred. This is an image sensor of the type that sequentially reads out using a CCD.

On the other hand, the CMOS image sensor is similar to the CCD image sensor in that photoelectric conversion elements corresponding to pixels are arranged two-dimensionally, but the vertical and horizontal transfer CCDs are not used for reading signals, and the CMOS device The signal stored for each pixel is read from the selected pixel by the selection line made of aluminum, copper wire, or the like.

As described above, the CCD image sensor and the CMOS image sensor have many different elements such as a reading method, but both have the common structure of the photodiode.

The maximum value of the signal charge amount that can be stored in the photoelectric conversion element is called the saturated signal charge amount (Qs). The image sensor having a high saturation signal charge amount has an improved dynamic range and SN ratio. Therefore, the increase of the saturation signal charge amount is a very important factor for improving the characteristics of the image sensor. As a method of increasing the saturation signal charge amount, increasing the area of the photodiode or increasing the PN junction capacitance of the photodiode can be considered.

Patent Document 1 proposes an imaging device capable of increasing the saturation signal charge amount and obtaining high sensitivity without increasing the area or impurity concentration of the photoelectric conversion device.

JP, 2005-332925, A

As described above, as a method of increasing the saturation signal charge amount, increasing the area of the photodiode or increasing the PN junction capacitance of the photodiode can be considered.

However, if the area of the photodiode is increased, the total number of pixels of the image sensor will decrease with the increase of the area of the photodiode when compared at the same angle of view. Further, if the concentration of the P-type region and the N-type region is increased in order to increase the PN junction capacitance of the photodiode, the dark current also increases, so there is a limit to increase the PN junction capacitance.

Further, Patent Document 1 discloses a technique of increasing the saturation signal charge by continuously extending the PN junction capacitance expanded portion from the substrate surface side in the substrate depth direction, but there is a restriction on the arrangement of the readout electrodes. There is a possibility that it may be difficult to select an optimum PN junction capacitance expansion pattern for giving priority to signal reading.

The present technology has been made in view of such a situation, and makes it possible to increase the saturation signal charge amount.

Imaging element to an embodiment of the present technology, in order in the depth direction from the top surface of the substrate to the semiconductor substrate, a first P-type impurity region, a first N-type impurity region, than the first N-type impurity regions with a low concentration of the first low-concentration N-type impurity region, and a capacity expansion portion that forms a PN junction surface and a second P-type impurity region and the second N-type impurity region, said first P -Type impurity region, the first N-type impurity region, and the first low-concentration N-type impurity region are stacked in the first direction, and the second P-type impurity region and the second N-type impurity region are stacked. Are stacked in a second direction different from the first direction, and the concentrations of the first N-type impurity region and the second N-type impurity region are higher than those of the first low-concentration N-type impurity region. Is also a high concentration .

A read electrode for reading accumulated charge is further provided on a surface of the first P-type impurity region facing a surface on which the second N-type impurity region is provided, and the capacitance expanding section includes the first electrode. Can be formed in a region farther from the read electrode than the N-type impurity region.

The second P-type impurity regions and the second N-type impurity regions may be alternately arranged in the capacitance expanding section.

A potential gradient may be provided from the capacitance expanding section to the read electrode in order to read the charge.

The second N-type impurity region in the capacitance expanding portion may be formed in a quadrangular shape in a cross-sectional view from a predetermined direction.

The second P-type impurity region in the capacitance expansion portion may be formed in a curved shape having a predetermined width in a cross-sectional view from a predetermined direction.

The second P-type impurity region in the capacitance expanding portion may be formed in a circular shape having a predetermined width in a cross-sectional view from a predetermined direction.

The repeating interval between the second P-type impurity region and the second N-type impurity region of the capacitance expanding portion may be 1 μm or less.

The floating diffusion can be shared by a plurality of image pickup devices, and the readout electrode can be arranged in the vicinity of the floating diffusion.

In the image sensor according to one aspect of the present technology, a semiconductor substrate is formed in order from the upper surface of the substrate in the depth direction by a first P-type impurity region, a first N-type impurity region, and a first N-type impurity region. Also, a first low-concentration N-type impurity region having a low concentration, and a capacitance expanding portion forming a PN junction surface from the second P-type impurity region and the second N-type impurity region are stacked. Further , the first P-type impurity region, the first N-type impurity region, and the first low-concentration N-type impurity region are stacked in the first direction, and the second P-type impurity region and the second N-type impurity region are stacked. The impurity regions are stacked in a second direction different from the first direction, and the concentrations of the first N-type impurity region and the second N-type impurity region are higher than those of the first low-concentration N-type impurity region. The concentration .

According to the embodiments of the present technology, it is possible to increase the saturation signal charge amount.

Note that the effects described here are not necessarily limited, and may be any effects described in the present disclosure.

It is a figure which shows an example of a structure of an image sensor. It is a figure which shows the relationship between depth and potential. It is a figure which shows an example of a structure of an image sensor. It is a figure which shows the relationship between depth and potential. It is a figure which shows an example of a structure of an image sensor. It is a figure which shows the relationship between depth and potential. It is a figure which shows an example of a structure of an image sensor. It is a figure which shows the relationship between depth and potential. It is a figure showing composition of one embodiment of an image sensor to which this art is applied. It is a figure for demonstrating the flow of an electric charge. It is sectional drawing of an image sensor. It is a figure for demonstrating arrangement|positioning of a read-out electrode. It is a figure which shows an example of the shape of the N+ area|region in a PN junction capacitance expansion part. It is a figure which shows an example of the shape of the N+ area|region in a PN junction capacitance expansion part. It is a figure which shows an example of the shape of the N+ area|region in a PN junction capacitance expansion part. It is a figure which shows an example of the shape of the N+ area|region in a PN junction capacitance expansion part. It is a figure which shows an example of the shape of the N+ area|region in a PN junction capacitance expansion part. It is a figure which shows an example of the shape of the N+ area|region in a PN junction capacitance expansion part. It is a figure which shows an example of the shape of the N+ area|region in a PN junction capacitance expansion part. It is a figure which shows an example of the shape of the N+ area|region in a PN junction capacitance expansion part. It is a figure which shows an example of the shape of the N+ area|region in a PN junction capacitance expansion part. It is a figure which shows an example of the shape of the N+ area|region in a PN junction capacitance expansion part. It is a figure which shows an example of the shape of the N+ area|region in a PN junction capacitance expansion part. It is a figure which shows an example of the shape of the N+ area|region in a PN junction capacitance expansion part. It is a figure which shows an example of the shape of the N+ area|region in a PN junction capacitance expansion part. It is a figure which shows an example of the shape of the N+ area|region in a PN junction capacitance expansion part. It is sectional drawing of the image pick-up element shown in FIG. It is a figure for demonstrating the size of 1 pixel. It is a figure for demonstrating the relationship between the size of a pixel, and the amount of saturation signal charges. It is a figure for demonstrating the size of the pixel which has a PN junction capacitance expansion part. It is a figure for demonstrating the relationship between the size of a pixel, and the amount of saturation signal charges. It is a figure for explaining other composition of an image sensor. It is a figure which shows the relationship between depth and potential. It is a figure for explaining other composition of an image sensor. It is a figure for demonstrating the structure of sharing between pixels. It is a figure for demonstrating the structure of sharing between pixels. It is a figure for demonstrating the structure of sharing between pixels. It is a figure which shows the usage example of an image sensor. It is a figure which shows the structure of an imaging device.

Below, the form (henceforth an embodiment) for carrying out this art is explained. The description will be given in the following order.
1. Image sensor configuration (conventional)
2. Configuration of image sensor 3. 3. Shape of N+ region of PN junction capacitance expansion part 4. 4. Improvement of saturation signal charge amount Other configurations of image sensor 6. Pixel sharing 7. Image sensor usage example

The present technology described below can be applied to an image pickup device that constitutes a CCD image sensor or a CMOS image sensor, and therefore, such an image pickup device will be described as an example here. Further, by applying the present technology described below, it is possible to increase the saturated signal charge amount (Qs) that is the maximum value of the signal charge amount that can be accumulated in the image sensor (photoelectric conversion element (photodiode)).

In order to describe the image pickup device to which the present technology that can obtain such effects is applied, first, for comparison, a conventional image pickup device will be briefly described.

<Structure of image sensor (conventional)>
FIG. 1 is a diagram showing a configuration of an example of an image sensor. The image pickup device 10 has a structure in which impurity regions of a P+ region 21, an N+ region 22, an N− region 23, and a P+ region 24 are formed in order from the upper surface of a silicon substrate in the depth direction, and the side surface has a P+ region. It has a structure formed by 25.

In FIG. 1 and the following description, the notations + and − such as the P+ region and the P− region indicate that the impurity concentration is higher and lower than the other regions.

When light is incident on the image sensor 10 having such a structure, electron-hole pairs are generated, and signal charges (electrons) are accumulated at the junction between the P-type region and the N-type region. A readout electrode 31 for reading out the accumulated charges is provided on the upper surface of the P+ region 21 in the image sensor 10 shown in FIG.

The relationship between the depth direction and the potential in the image sensor 10 having the structure shown in FIG. 1 is shown in FIG. In FIG. 2, the horizontal axis represents the depth from the upper surface of the image sensor 10 (the upper surface of the P+ region 21), and the vertical axis represents the negative potential. In FIG. 2, the larger the value on the vertical axis (lower negative potential), the higher the potential for electrons and the lower potential for holes.

In the following description, the structure of the image sensor 10 shown in FIG. 1 is used as a reference, and the image sensor 10 having the potential state shown in FIG. Will be added.

3, 5, and 7 are diagrams showing an example of a conventional image sensor having a structure for increasing the saturation signal charge amount (Qs) with respect to the image sensor 10 shown in FIG. In the following description, parts having the same configurations as those of the image sensor 10 shown in FIG. 1 are designated by the same reference numerals, and the description thereof will be omitted as appropriate.

The image pickup device 50 shown in FIG. 3 has a structure in which the region of the N+ region 22 is made larger (the depth is made deeper) than that of the reference image pickup device 10 shown in FIG. The N+ region 61 of the image sensor 50 is provided to a position deeper than the N+ region 22 of the image sensor 10 (FIG. 1).

FIG. 4 is a diagram showing the relationship between the depth direction and the potential in the image sensor 50 having the structure shown in FIG. 4, the dotted line represents the potential state in the image sensor 10 shown by the solid line in FIG. 2, and the solid line represents the potential state in the image sensor 50.

By deepening the N+ region 61 as in the image pickup device 50, the potential in the deep portion of the bulk can be deepened and capacitance can be added. As shown in FIG. 4, by adding capacitance, it is possible to maintain a state in which the negative potential is low (peak state) in the depth direction, and increase the saturation signal charge amount (Qs). Is possible.

However, in this case, there is a possibility that all the signals cannot be read when the read gate is turned on because the electric field in the image sensor is insufficient or a barrier is generated.

FIG. 5 is a diagram showing another configuration of the image sensor. The image pickup device 100 shown in FIG. 5 has a structure in which the impurity concentration of the N+ region 22 is higher than that of the reference image pickup device 10 shown in FIG. The N++ region 101 of the image sensor 100 has a higher impurity concentration than the N+ region 22 of the image sensor 10 (FIG. 1).

FIG. 6 is a diagram showing the relationship between the depth direction and the potential in the image sensor 100 having the structure shown in FIG. In FIG. 5, the dotted line represents the potential state in the image sensor 10 shown by the solid line in FIG. 2, and the solid line represents the potential state in the image sensor 100.

By increasing the impurity concentration of the N++ region 101 joined to the P+ region 21 like the image pickup device 100, the surface of the image sensor can be deepened and capacitance can be added to the surface. As shown in FIG. 6, by providing the capacitance, the negative potential at the peak can be made higher, and the saturation signal charge amount (Qs) can be increased.

However, since it is necessary to increase the voltage for reading, there is a possibility that reading failure may occur or white spots may worsen.

FIG. 7 is a diagram showing another configuration of the image sensor. The image pickup device 150 shown in FIG. 7 has a structure in which the P+ region 21 is thinner (shallow) and the N+ region 22 is thicker (deeper) than the reference image pickup device 10 shown in FIG. .. The P+ region 151 of the image sensor 150 is made thinner (shallow) than the P+ region 21 of the image sensor 10 (FIG. 1), and the N+ region 152 of the image sensor 150 is the N+ region 22 of the image sensor 10 (FIG. 1). It is made thicker (deeper) than.

FIG. 8 is a diagram showing the relationship between the depth direction and the potential in the image sensor 150 having the structure shown in FIG. In FIG. 7, the dotted line represents the potential state in the image sensor 10 shown by the solid line in FIG. 2, and the solid line represents the potential state in the image sensor 150.

By expanding the N+ region 152 to the silicon substrate surface side like the image pickup device 150, the depth at which the potential peak starts can be brought to a shallow position as shown in FIG. It becomes possible to increase the quantity (Qs).

However, as in the image sensor 100 shown in FIG. 5, white spots may be deteriorated due to an increase in the surface electric field.

Therefore, an image pickup device having a structure capable of increasing the saturation signal charge amount (Qs) and preventing the white spots from being deteriorated and the read failure not occurring will be described below.

<Structure of image sensor>
FIG. 9: is a figure which shows the structure of one Embodiment of the image pick-up element to which this technique is applied.

In the image sensor 300 shown in FIG. 9, parts having the same configurations as those of the image sensor 10 shown in FIG. 1 are denoted by the same reference numerals, and the description thereof will be omitted as appropriate. In the image sensor 300 shown in FIG. 9, compared with the image sensor 10 shown in FIG. 1, the region of the N− region 23 is composed of an N− region 301, an N+ region 302, and a P+ region 303. , But other parts are the same.

In the image sensor 300, the low-concentration N− region 301 provided below the high-concentration N+ region 22 is configured to have a shallow depth, and between the N− region 301 and the high-concentration P+ region 24. , N+ region 302 and P+ region 303 are formed. Here, the layer formed of the N+ region 302 and the P+ region is described as a PN junction capacitance expanding portion 310. Since the PN junction capacitance expansion unit 310 is a portion provided to expand the signal charge storage unit of the image sensor 300, it will be described as a capacitance expansion unit here.

In the example shown in FIG. 9, the PN junction capacitance expanding unit 310 includes an N+ region 302-1, an N+ region 302-2, an N+ region 302-3, a P+ region 303-1 and a P+ region 303-2, and an N+ region. A P+ region 303-1 is formed between the 302-1 and the N+ region 302-2, and a P+ region 303-2 is formed between the N+ region 302-2 and the N+ region 302-3. There is.

As described above, the PN junction capacitance expanding portion 310 has a configuration in which the N+ regions 302 (N-type impurity regions) and the P+ regions 303 (P-type impurity regions) are alternately arranged.

The pitch interval of the PN junction capacitance expanding portion 310, in other words, the repeating interval of the N+ region 302 and the P+ region 303 is preferably configured to be 1.0 μm or less, for example. For example, the combined width of the N+ region 302-1 and the P+ region 303-1 is 1.0 μm or less. By making the pitch interval smaller and finer, the concentration of N-type impurities that are deposited in between is increased, and the saturation signal charge amount (Qs) can be further increased.

As will be described later, the pitch intervals of the PN junction capacitance expanding portions 310 may be uniform as in the image sensor 300 shown in FIG. 9 or may be non-uniform. In addition, here, the description will be continued assuming that the repeating interval between the N+ region 302 and the P+ region 303 is, for example, 1.0 μm or less, but this is not a description that limits the application range of the present technology, and other intervals may also be used. Can be applied. For example, the present technology can be applied even when the thickness is 1.0 μm or more.

Assuming that the N+ region 22 and the N− region 301 are laterally provided layers, the N+ region 302 and the P+ region 303 of the PN junction capacitance expansion part 310 are vertically provided layers. The PN junction capacitance expanding portion 310 has a configuration in which N+ regions 302 and P+ regions 303 are alternately stacked in the vertical direction, and is a layer stacked in a direction different from other layers.

Further, the PN junction capacitance expanding section 310 has a potential gradient as shown in FIG. 10 is a diagram showing the image pickup device 300 as in FIG. 9, and is a diagram showing the flow of signal charges in the image pickup device 300 by arrows.

As indicated by the arrow, each of the charge generated in the N+ region 302-1, the charge generated in the N+ region 302-2, and the charge generated in the N+ region 302-3 is made to go close to the read electrode 31. , There is a potential gradient. In other words, a potential gradient for reading charges is provided between the PN junction capacitance expansion portion 310 and the read electrode 31.

FIG. 11 shows a view of the image sensor 300 shown in FIG. 9 when viewed from the top. FIG. 11A is a cross-sectional view of the image sensor 300, like the image sensor 300 shown in FIG. In the image pickup device 300 shown in FIG. 11A, the PN junction capacitance expansion part 310 of the image pickup device 300 shown in FIG. 9 is also described as the PN junction capacitance expansion part 310, but the N+ region 22 and the N− region 301 are referred to. Collectively, the N-type impurity region 320 is described, and the P+ region 21 is described as the P-type impurity region 330.

As shown in FIG. 11A, the image sensor 300 has a structure in which a P-type impurity region 330, an N-type impurity region 320, and a PN junction capacitance expansion portion 310 are stacked in this order from the side where the readout electrode 31 is provided. ing.

The P-type impurity region 330 and the N-type impurity region 320 are laterally stacked layers, and the PN junction capacitance expanding portion 310 is in a direction different from the layers of the P-type impurity region 330 and the N-type impurity region 320. In the direction shown in FIG. 11A, the N+ region 302 and the P+ region 303 are laminated in the vertical direction.

In this way, the PN junction capacitance expansion portion 310 can be a layer stacked in a direction different from that of other layers. The different direction may be a direction perpendicular to the other layers or a direction (oblique direction) intersecting at a predetermined angle.

FIG. 11B is a cross-sectional view of the image pickup device 300 shown in FIG. 11A taken along the line A-A′. FIG. 11C is a sectional view taken along the line B-B′. That is, FIG. 11B is a cross-sectional view of the N-type impurity region 320, and FIG. 11C is a cross-sectional view of the PN junction capacitance expansion portion 310.

As shown in FIG. 11B, the cross-sectional view of the N-type impurity region 320 is a surface on which the N-type impurities are uniformly diffused. The read electrode 31 is also shown in FIG. 11B for reference. The readout electrode 31 is arranged so as to cover a partial region of the N-type impurity region 320.

In the image sensor 300 to which the present technology is applied, the arrangement position of the readout electrode 31 is not limited, and the readout electrode 31 can be arranged at various positions as shown in FIG. Referring to FIG. 12, as in the case shown in FIG. 11B, the read electrode 31-1 can be provided on the right side of the N-type impurity region 320 in the figure. Further, as shown in FIG. 12, the read electrode 31-2 may be provided on the lower side of the N-type impurity region 320 in the figure.

As shown as the read electrode 31-1 and the read electrode 31-2, not only the arrangement but also the size of the read electrode has a high degree of freedom, and the present technology can be applied to any size. Further, as shown in FIG. 12, the read electrode 31-3 may be provided at a corner portion of the N-type impurity region 320. Further, as shown in FIG. 12, the read electrode 31-4 may be provided in the central portion of the N-type impurity region 320.

The readout electrode 31 is arranged at any of the positions shown as the readout electrodes 31-1 to 31-4. Note that the read electrode 31 may be arranged in a portion other than the read electrode 31 shown in FIG.

According to the present technology, the structure for increasing the saturation signal charge amount (Qs) is not the structure near the surface of the substrate as in the image sensor described with reference to FIGS. Since it is on the side, the read electrode 31 arranged on the surface of the substrate can be arranged at a desired position without limitation, as described above. That is, since there is no influence of the PN junction capacitance expanding portion 310, there is no restriction on the read electrode 31.

Reference is made to FIG. 11C. FIG. 11C is a cross-sectional view of the PN junction capacitance expansion portion 310. The cross section of the PN junction capacitance expansion portion 310 is in a state where N+ regions 302 and P+ regions 303 are alternately arranged. In the example shown in FIG. 11C, the N+ regions 302 of the PN junction capacitance expanding portion 310 are provided in a grid shape and are provided in a distributed manner in 16 quadrangles.

Although the size of one quadrangle may be any size, for example, as described above, it is 1.0 μm or less (the total size of the quadrangular N-type region and the adjacent P-type region is 1.0 μm or less. ) Is preferable. Further, although the shape is a quadrangle, the shape may be a square, a rectangle, a rhombus, a trapezoid, or a shape other than a quadrangle such as a circle or an ellipse.

<Regarding the shape of the N+ region of the PN junction capacitance expansion part>
Here, the shape of the N+ region 302 of the PN junction capacitance expanding portion 310 will be further described with reference to FIGS. 13 to 26. 13 to 26 are sectional views of the PN junction capacitance expansion portion 310, as in FIG. 11C. In addition, in FIGS. 13 to 26, the read electrode 31 is also illustrated for the sake of explanation.

Also, the shape of the N+ region 302 of the PN junction capacitance expanding portion 310 will be described as an example, but basically the same is true when the shape of the P+ region 303 of the PN junction capacitance expanding portion 310 is described as an example. Therefore, here, the description will be continued taking the N+ region 302 as an example.

The N+ region 302 of the PN junction capacitance expansion portion 310 shown in FIG. 13 is provided in a grid shape like the N+ region 302 shown in FIG. 11C, but one quadrangle is small and 28 quadrangles are dispersed. Are provided. In addition, each N+ region 302 is formed so as to be in contact with each other at a corner portion. In this way, the N+ region 302 of the PN junction capacitance expanding portion 310 may be provided in a lattice shape, and one lattice may be formed small.

The N+ region 302 of the PN junction capacitance expanding portion 310 shown in FIG. 14 is provided in a grid shape like the N+ region 302 shown in FIG. 11C, but one square is large and dispersed in four squares. Are provided. In this way, the N+ region 302 of the PN junction capacitance expanding portion 310 may be provided in a lattice shape, and one lattice may be formed large.

Note that, as described above, the N+ region 302 of the PN junction capacitance expanding portion 310 shown in FIG. 14 is shown in a state where the pitch interval of the PN junction capacitance expanding portion 310 satisfies the condition of preferably 1.0 μm or less. When 1 is applied, if one pixel is small, the N+ region 302 can be formed while satisfying the condition. That is, the size of the N+ region 302 of the PN junction capacitance expanding portion 310 can be set by the size of one pixel.

The N+ region 302 of the PN junction capacitance expansion portion 310 shown in FIG. 15 is provided in a grid shape like the N+ region 302 shown in FIG. 11C, but is arranged in the region where the read electrode 31 is arranged. The existing N+ region 302 is formed larger than the N+ regions 302 arranged in other regions. As described above, the shapes and sizes of the individual N+ regions 302 in the PN junction capacitance expansion portion 310 do not have to be the same.

The shape of the N+ region 302 of the PN junction capacitance expansion portion 310 shown in FIG. 16 is such that the P+ regions 303 are discretely formed in a lattice shape and fill the space between them. The N+ region 302 has a shape such that the N+ region 302 is connected to other portions than the P+ region 303. As shown in FIG. 16, the N+ region 302 does not have to have a shape in which the individual N+ regions 302 are formed without being connected to each other, as shown in FIG. 15, for example.

The N+ region 302 of the PN junction capacitance expansion portion 310 shown in FIG. 17 has the same shape as the N+ region 302 shown in FIG. 16, but the N+ region 302 arranged in the region where the read electrode 31 is arranged. Is formed larger than the N+ region 302 arranged in another region, and the P+ region 303 is not provided in that region.

The shape of the N+ region 302 of the PN junction capacitance expansion portion 310 shown in FIG. 18 is a rectangle. The N+ region 302 shown in FIG. 18 is formed in a rectangular shape, and the long side of the rectangular shape is formed in the direction parallel to the read electrode 31.

The N+ region 302 of the PN junction capacitance expansion portion 310 shown in FIG. 19 is formed in the same rectangular shape as the N+ region 302 shown in FIG. 18, but its direction is different. The N+ region 302 shown in FIG. 19 is formed in a rectangular shape, and the long side of the rectangular shape is formed in the direction orthogonal to the read electrode 31.

The N+ region 302 of the PN junction capacitance expansion portion 310 shown in FIG. 20 is formed in the same rectangular shape as the N+ region 302 shown in FIG. 19, but its size is different. The N+ region 302 shown in FIG. 20 is formed in a rectangular shape so that the long side of the rectangle comes in a direction orthogonal to the read electrode 31, and a P+ region 303 is provided between the N+ regions 302. There is.

As shown in FIGS. 18 to 20, the shape of the N+ region 302 may be a rectangle, and the long side direction of the rectangle is orthogonal to the direction parallel to the read electrode 31. It may be in the direction of doing.

The N+ region 302 of the PN junction capacitance expansion part 310 shown in FIG. 21 has a predetermined width within the region of the PN junction capacitance expansion part 310 and is a P+ region 303 provided in a linear shape in an oblique direction. It is shaped so as to fill the other areas.

The N+ region 302 of the PN junction capacitance expanding portion 310 shown in FIG. 22 has a predetermined width within the region of the PN junction capacitance expanding portion 310 and is provided in a curved shape (including a part of a linear shape). It is shaped so as to fill the area other than the existing P+ area 303.

The N+ region 302 of the PN junction capacitance expanding portion 310 shown in FIG. 23 has a predetermined width further than the N+ region 302 shown in FIG. 22 and is provided in a linear shape in an oblique direction and a lateral direction. It is provided in the region excluding the P+ region 303.

The N+ region 302 of the PN junction capacitance expansion part 310 shown in FIG. 24 has a predetermined width in the region of the PN junction capacitance expansion part 310 and is a P+ region 303 provided in a wave shape (curve shape). It is shaped so as to fill the other areas.

The N+ region 302 of the PN junction capacitance expansion part 310 shown in FIG. 25 has a predetermined width within the region of the PN junction capacitance expansion part 310 and fills a region other than the P+ region 303 provided in a circular shape. It is shaped like this.

The N+ region 302 of the PN junction capacitance expanding portion 310 shown in FIG. 26 is a region within the region of the PN junction capacitance expanding portion 310, except for the P+ region 303 having a predetermined width and provided in a spiral shape. It is shaped to fill.

As described above, as the shape of the N+ region 302 of the PN junction capacitance expanding portion 310 (the shape of the P+ region 303 of the PN junction capacitance expanding portion 310), various shapes such as a lattice shape, a rod shape, and a curved line can be adopted. is there. Further, it may be line-symmetric, point-symmetric, or asymmetric.

Note that the shapes shown in FIG. 11C and FIGS. 13 to 26 are examples, and are not limitative, and other shapes are within the scope of application of the present technology.

However, a shape that satisfies the following conditions is preferable. As described above, the pitch interval of the PN junction capacitance expanding portions 310 is configured to be 1.0 μm or less. Further, in the PN junction capacitance expanding portion 310, the ratio of the N+ region 302 and the P+ region 303 is the same (1:1), or the N+ region 302 has a slightly higher ratio than the P+ region 303.

In the following description, the description will be continued by exemplifying the configuration of the PN junction capacitance expanding unit 310 shown in FIG. 11C.

<Improvement of saturation signal charge amount>
With the structure in which the P-type impurity region 330, the N-type impurity region 320, and the PN junction capacitance expansion portion 310 are stacked as in the above-described image sensor 300, it is possible to improve the saturation signal charge amount. Here, description will be added regarding the fact that the saturation signal charge amount is improved.

FIG. 27 shows the configuration of the reference image pickup device 10 (the image pickup device 300 to which the present technology is applied and the image pickup device shown for comparison) shown in FIG. 1 again. In order to compare the image pickup device 10 shown in FIG. 27 with the image pickup device 300 shown in FIG. 11, FIG. 27A shows a side sectional view, and FIG. 27B shows the image pickup device 10 shown in FIG. A sectional view taken along line BB′ is shown in FIG. 27C, and a sectional view taken along line BB′ of the image pickup device 10 shown in FIG. 27A is shown in FIG. 27C. Note that the read electrode 31 is also illustrated in FIG. 27B for reference.

FIG. 27A is a cross-sectional view of the image pickup device 10, like the image pickup device 10 shown in FIG. 1. In the image sensor 10 shown in FIG. 27A, the P+ region 21 of the image sensor 10 shown in FIG. 1 is described as a P-type impurity region 410, and the N+ region 22 and the N− region 23 are collectively referred to as an N-type impurity region 420. Write.

Since the image pickup device 10 has no region corresponding to the PN junction capacitance expansion part 310, it has a structure in which a P-type impurity region 410 and an N-type impurity region 420 are stacked, as shown in FIG. 27A.

FIG. 27B is a cross-sectional view of the image sensor 10 shown in FIG. 27A taken along the line A-A′. FIG. 27C is a sectional view taken along the line B-B′. In the case of the image pickup device 10, FIGS. 27B and 27C are cross-sectional views taken at different positions, but both views are cross-sectional views in the N-type impurity region 420.

That is, as shown in FIGS. 27B and 27C, the cross section of the N-type impurity region 420 is a surface in which N-type impurities are uniformly diffused.

The relationship between the size of the image sensor 10 having such a configuration and the saturation signal charge amount will be described with reference to FIGS. 28 and 29.

FIG. 28 is a cross-sectional view of the image sensor 10 when viewed from the top, and is a cross-sectional view of the image sensor 10 taken along line A-A′ or B-B′ shown in FIG. 27B or 27C. 28A, 28B, and 28C respectively configure 1 pixel, 4 pixels, and 16 pixels in 4 μm×4 μm, and each pixel corresponds to the configuration of the image sensor 10 shown in FIG. 1 (FIG. 27). The case where it has is shown.

The image sensor 10 shown in FIG. 28A has one pixel in 4 μm×4 μm, and thus one pixel has a size of 4 μm×4 μm. Hereinafter, the image pickup device 10 having a size of 4 μm×4 μm is referred to as a state A.

The image sensor 10 shown in FIG. 28B has 4 pixels in 4 μm×4 μm, and thus one pixel has a size of 2 μm×2 μm. Hereinafter, the image pickup device 10 having a size of 2 μm×2 μm is referred to as a state B. The image sensor 10 shown in FIG. 28C has 16 pixels in 4 μm×4 μm, and thus one pixel has a size of 1 μm×1 μm. Hereinafter, the image pickup device 10 having a size of 1 μm×1 μm is referred to as a state C.

FIG. 29 is a graph showing a change in saturation when the same potential is realized for each of the image pickup devices 10 in the states A, B, and C. In the graph shown in FIG. 29, the horizontal axis represents the minimum unit cell size (size of one pixel), and the vertical axis represents the saturated signal charge amount per unit area. Further, in the graph shown in FIG. 29, the saturated signal charge amount per unit area in each of the states A, B, and C is shown in dots (A, B, and C are shown in circles). There is.

To compare the saturated signal charge amount per unit area of the image pickup device 10 in the state A and the saturated signal charge amount per unit area of the image pickup device 10 in the state B, the saturated signal charge amount per unit area of the state A is , The saturated signal charge amount per unit area in the state B is larger. To compare the saturated signal charge amount per unit area of the image pickup device 10 in the state A and the saturated signal charge amount per unit area of the image pickup device 10 in the state C, the saturated signal charge amount per unit area of the state C is better. , And the saturated signal charge amount per unit area in the state A is larger. In order to compare the saturated signal charge amount per unit area of the image pickup device 10 in the state B and the saturated signal charge amount per unit area of the image pickup device 10 in the state C, This is larger than the saturated signal charge amount per unit area in the state B.

The change from the state A to the state B is that the pixel size is reduced and the PN junction capacitance is expanded. With such a change, it is considered that the area of the P-type impurity region increases and the amount of the N-type impurity region relatively decreases, and due to the influence, the saturation signal charge amount per unit area decreases. The change from the state B to the state C is that the pixel size becomes smaller. With such conversion, the N-type impurity region decreases, but it is considered that the saturation signal charge amount per unit area increases due to the influence of the increase in the PN junction capacitance.

From these relationships, it can be seen that as the pixel size is miniaturized, the saturated signal charge amount per unit area tends to increase. However, if the pixel size is not miniaturized with an appropriate value, the saturation per unit area is saturated. It can be seen that the signal charge amount may not increase.

Specifically, by setting the pixel size to 1.0 μm or less, the saturated signal charge amount per unit area can be increased. Therefore, as described above, the pitch interval of the PN junction capacitance expanding portions 310 of the image sensor 300 to which the present technology is applied is set to 1.0 μm or less, for example.

When the size of the image pickup device 300 to which the present technology is applied is configured to be 4 μm×4 μm, the configuration shown in FIG. 30 is obtained. FIG. 30A is similar to the view shown in FIG. 11B and is a cross-sectional view of the image pickup device 300 shown in FIG. 11A taken along line A-A′. FIG. 30B is a cross-sectional view of the image pickup device 300 shown in FIG. 11A taken along line B-B′. Note that the read electrode 31 is also illustrated in FIG. 30B for reference.

The image sensor 300 shown in FIG. 30A is a cross section of the N-type impurity region 320, and the N-type impurity region 320 for one pixel is formed in 4 μm×4 μm. The N-type impurity region 320 having a size of 4 μm×4 μm is in a state D.

The image pickup device 300 shown in FIG. 30B is a cross section of the PN junction capacitance expansion portion 310, and 16 N+ regions 302 of 1 μm×1 μm (more accurately, 1 μm×1 μm or less) are formed in 4 μm×4 μm. ing. A state in which 16 N+ regions 302 of 1 μm×1 μm are formed in 4 μm×4 μm is referred to as a state E.

The imaging device 300 has the N-type impurity region 320 in the state D on the side of the read electrode 31, and the PN junction capacitance expansion portion 310 in the state E on the side farther from the read electrode 31 (deep portion of the substrate). is doing. That is, the image sensor 100 has a configuration in which the state D and the state E are different in one pixel.

State D (FIG. 30A) is the same as state A (FIG. 28A), and state E (FIG. 30B) is the same as state C (FIG. 28C). The image pickup device 300 has the same structure as one pixel on the side closer to the readout electrode 31, but has the same structure as a miniaturized pixel on the far side.

FIG. 31 is a graph showing changes in saturation when the same potential is realized for the image pickup devices 10 in the states A, B, and C shown in FIG. 29, and the saturation per unit area of the image pickup device 300 is shown. It is a graph which added the signal charge amount.

As described with reference to FIG. 30, the image sensor 300 has a configuration of state D (FIG. 30A) as a pixel and functions as one pixel having a size of 4 μm×4 μm. In FIG. 31, as the state D, the saturated signal charge amount per unit area is illustrated.

Referring to FIG. 31, the image pickup device 300 has the same size as the image pickup device 10 in the state A, but the saturated signal charge amount per unit area is almost the same as the image pickup device 10 in the state C. There is. As described above, according to the image pickup device 300, it is possible to significantly increase the saturation signal charge amount as compared with an image pickup device of the same size to which the present technology is not applied.

<Other configuration of image sensor>
Another configuration of the image sensor will be described.

FIG. 32 is a diagram showing another configuration of the image sensor to which the present technology is applied. The basic configuration of the image sensor 500 shown in FIG. 32 is the same as that of the image sensor 300 shown in FIG. 9, but the N+ region 22 is not provided, and the N− region 501 is the only N-type impurity region. The points are different. The image sensor 500 is configured to have a low concentration of N-type impurities on the read electrode 31 side. The image pickup device 500 also includes the PN junction capacitance expansion portion 310 at a position deeper than the N− region 501.

As described above, by making the concentration of the N-type impurity on the read electrode 31 side thin, the potential can be made shallow. FIG. 33 is a diagram showing the relationship between the depth direction and the potential in the image sensor 500 having the structure shown in FIG. In FIG. 33, the dotted line represents the potential state in the image sensor 10 shown by the solid line in FIG. 2, and the solid line represents the potential state in the image sensor 500.

By setting the concentration of the N-type impurity on the read electrode 31 side to be low like the image sensor 500, the depth at which the potential peak starts can be brought to a shallow position as shown in FIG.

Further, since the image pickup device 500 has the PN junction capacitance expansion part 310, it is possible to increase the saturation signal charge amount similarly to the image pickup device 300.

By arranging the PN junction capacitance expanding portion 310 on the substrate side farther from the readout electrode 31 (the deep side of the substrate), the saturation signal charge amount can be improved. For example, when it is sufficient to secure the saturation signal charge amount obtained by the image sensor 10 shown in FIG. 1, the surface electric field is reduced by making the potential on the surface side of the substrate shallow as in the image sensor 500 shown in FIG. Can be alleviated and white spots can be improved.

In addition, since the potential becomes shallower, the read-out capability of the read-out electrode 31 can be improved, and the generated charge can be read out without being missed. Further, since the read voltage can be reduced due to the shallow potential, power consumption can be reduced.

FIG. 34 is a diagram showing still another configuration of the image sensor to which the present technology is applied. The structure of the image sensor 600 shown in FIG. 34 is the same as the structure of the image sensor 300 shown in FIG. 9, but the material forming the PN junction capacitance expansion portion 310 (FIG. 9) is different.

The PN junction capacitance expanding portion 610 of the image sensor 600 shown in FIG. 34 is composed of an N+ region 302 and a P+ corresponding region 601. The P+ corresponding region 601 is a region corresponding to the P+ region 303 of the PN junction capacitance expanding portion 310 of the image sensor 300 shown in FIG. The P+ region 601 is a region filled with an insulating film other than impurities, for example, a material used as an oxide film.

As a material that can be filled in the P+ corresponding region 601, when the imaging device 600 is formed of a silicon substrate, a material that can fill the interface with silicon with holes by a work function may be used.

The P+ corresponding region 601 is formed by forming a groove using a technique such as etching when the imaging device 600 is manufactured, and filling the groove with an insulating film, for example, a material that is also used as an oxide film. ..

In addition, in the case of using a technique such as etching, after the P+ region 24 is formed, a groove is formed by digging from the P+ region 24 side to the N− region 301, and the P+ corresponding region 601 is formed in the groove. The P+ corresponding region 601 can be formed by filling the material to be formed. When the P+ corresponding region 601 is formed in this way, as shown in FIG. 34, the P+ corresponding region 601 is also formed in the P+ region 24.

<About pixel sharing>
In the above-described embodiment, one image pickup device has been described as an example. For example, the image sensor 300 is used by being arranged in a pixel array section in a two-dimensional array of m rows and n columns. When a plurality of image pickup devices 300 are arranged, a floating diffusion (FD) may be shared by a plurality of pixels, for example, 2 pixels or 4 pixels. The technology of sharing between pixels can be applied also to the image sensor to which the present technology is applied.

FIG. 35 shows an image sensor for four pixels arranged in the pixel array portion in the horizontal direction. FIG. 35A is a diagram illustrating a case where the image pickup device 300 illustrated in FIG. 9 (FIG. 11A) is arranged in the horizontal direction by four pixels. In each of the image pickup devices 300-1 to 300-4, read-out electrodes 31-1 to 31-4 are arranged on the front surface side of the substrate, and PN junction capacitance expanding sections 310-1 to 310-4 are arranged on the deep side of the substrate. It is arranged.

FIG. 35B is a diagram illustrating a case where the image sensor 600 illustrated in FIG. 34 is arranged in the horizontal direction by four pixels. In each of the image pickup devices 600-1 to 600-4, read-out electrodes 31-1 to 31-4 are arranged on the front surface side of the substrate, and PN junction capacitance expanding sections 610-1 to 610-4 are arranged on the deep side of the substrate. It is arranged.

Of the image pickup device 300 and the image pickup device 600 shown in FIGS. 35A and 35B (hereinafter, the image pickup device 300 will be described as an example), the read electrode 31 of the adjacent image pickup device 300 is arranged at a close position. ing.

For example, the read electrode 31-1 and the read electrode 31-2 of the adjacent image pickup device 300-1 and image pickup device 300-2 are arranged in close proximity to each other. Similarly, the read-out electrodes 31-3 and 31-4 of the adjacent image pickup device 300-3 and the image pickup device 300-4 are arranged in close proximity to each other.

Further, the image pickup device 300-1 and the image pickup device 300-2 arranged adjacent to each other share one floating diffusion (FD) 701-1. Similarly, the image pickup device 300-3 and the image pickup device 300-4 arranged adjacent to each other share one floating diffusion (FD) 701-2.

The floating diffusion 701-1 is provided between the read electrode 31-1 and the read electrode 31-2. Further, the floating diffusion 701-1 is provided so as to straddle the P-type impurity region 330-1 and the P-type impurity region 330-2. Note that, in FIG. 35A, a line is added between the P-type impurity region 330-1 and the P-type impurity region 330-2 to clarify the boundary, but the line is added for the sake of description, and the actual P There is no such boundary line between the type impurity region 330-1 and the P type impurity region 330-2.

Similarly, the floating diffusion 701-2 is provided between the read electrode 31-3 and the read electrode 31-4. Further, the floating diffusion 701-2 is provided so as to straddle the P-type impurity region 330-3 and the P-type impurity region 330-4.

FIG. 36 is a view of the image pickup device 300 shown in FIG. 35A when viewed from above, and is a cross-sectional view of a portion of the PN junction capacitance expansion portion 310. The read electrode 31 is also shown for the sake of explanation. In FIG. 36, the image sensor 300 for 4 pixels of 2×2 is shown.

The image pickup device 300-1 (PN junction capacitance expansion part 310-1) and the image pickup device 300-2 (PN junction capacitance expansion part 310-2) are laterally adjacent to each other, and these two pixels form one floating diffusion. (FD) 701-1 is shared. The floating diffusion 701-1 is arranged between the read electrode 31-1 of the image sensor 300-1 and the read electrode 31-2 of the image sensor 300-2.

Similarly, the image pickup device 300-11 (PN junction capacitance expansion part 310-11) and the image pickup device 300-12 (PN junction capacitance expansion part 310-12) are laterally adjacent to each other, and one pixel is formed by these two pixels. Floating diffusion 701-11 is shared. The floating diffusion 701-11 is arranged between the read electrode 31-11 of the image sensor 300-11 and the read electrode 31-12 of the image sensor 300-12.

As described above, it is possible to adopt a configuration in which two adjacent pixels share one floating diffusion 701.

It is also possible to adopt a configuration in which one floating diffusion 701 is shared by four pixels. FIG. 37 shows the image sensor 300 in the case where one floating diffusion 701 is shared by four pixels.

Like FIG. 36, FIG. 37 shows an image sensor 300 for 4 pixels of 2×2. Since one floating diffusion 701 is shared by these four pixels, as shown in FIG. 37, the floating diffusion 701 is arranged in the central portion of the four pixels.

The readout electrode 31-1 of the image pickup device 300-1 (PN junction capacitance expansion part 310-1) and the readout electrode 31 of the image pickup device 300-2 (PN junction capacitance expansion part 310-2) so as to surround the floating diffusion 701. -2, the readout electrode 31-11 of the image pickup device 300-11 (PN junction capacitance expansion part 310-11) and the readout electrode 31-12 of the image pickup device 300-12 (PN junction capacitance expansion part 310-12) are arranged. There is.

As described above, it is also possible to adopt a configuration in which one floating diffusion 701 is shared by the four adjacent pixels.

According to the present technology, as described above, the degree of freedom in the arrangement position of the readout electrode 31 is high, and when one floating diffusion 701 is shared by two pixels or four pixels as described above, the readout is performed at an appropriate position. The electrode 31 can be arranged.

According to the present technology, as described above, the saturation signal charge amount in the image sensor can be improved. Further, even when the saturation signal charge amount is improved, the size does not become larger than that of the conventional image pickup device, and the size can be set to the same size or smaller.

<Example of use of image sensor>
FIG. 38 is a diagram showing a usage example of the above-described image sensor.

The above-described image sensor can be used in various cases for sensing light such as visible light, infrared light, ultraviolet light, and X-rays as described below.

-A device that captures images used for viewing, such as a digital camera or a portable device with a camera function.-For driving in front of a car, for safe driving such as automatic stop, and recognition of the driver's condition. Devices used for traffic, such as in-vehicle sensors that take images of the rear, surroundings, and inside the vehicle, surveillance cameras that monitor running vehicles and roads, ranging sensors that perform distance measurement between vehicles, etc. Devices used for home appliances such as TVs, refrigerators, and air conditioners to take images and operate the devices according to the gestures ・Endoscopes, devices that take blood vessels by receiving infrared light, etc. Used for medical care and healthcare ・Security devices such as security surveillance cameras and person authentication cameras ・Skin measuring devices for skin and scalp A device used for beauty, such as a microscope, a device used for sports, such as an action camera or wearable camera for sports purposes, a camera used for monitoring the condition of fields or crops, Equipment used for agriculture

39 is a block diagram showing a configuration example of an imaging device (camera device) 1000 which is an example of an electronic device to which the present technology is applied.

As shown in FIG. 39, the image pickup apparatus 1000 includes an optical system including a lens group 1001 and the like, an image pickup element 1002, a DSP 1003 as a camera signal processing unit, a frame memory 1004, a display unit 1005, a recording unit 1006, an operation unit 1007, and , A power supply unit 1008 and the like. The DSP 1003, the frame memory 1004, the display unit 1005, the recording unit 1006, the operation unit 1007, and the power supply unit 1008 are connected to each other via a bus line 1009.

The lens group 1001 takes in incident light (image light) from a subject and forms an image on the image pickup surface of the image pickup element 1002. The image sensor 1002 converts the amount of incident light imaged on the imaging surface by the lens group 1001 into an electric signal for each pixel and outputs the electric signal as a pixel signal.

The display unit 1005 includes a panel type display device such as a liquid crystal display device or an organic EL (electro luminescence) display device, and displays a moving image or a still image captured by the image sensor 1002. The recording unit 1006 records the moving image or the still image captured by the image sensor 1002 on a recording medium such as a memory card, a video tape, or a DVD (Digital Versatile Disk).

The operation unit 1007 issues operation commands for various functions of the image pickup apparatus 1000 under the operation of the user. The power supply unit 1008 appropriately supplies various power supplies serving as operation power supplies of the DSP 1003, the frame memory 1004, the display unit 1005, the recording unit 1006, and the operation unit 1007 to these supply targets.

Such an imaging device 1000 is applied to a video camera, a digital still camera, and a camera module for mobile devices such as smartphones and mobile phones. Then, in the image pickup apparatus 1000, the image pickup element according to each of the above-described embodiments can be used as the image pickup element 1002. Thereby, the image quality of the image pickup apparatus 1000 can be improved.

In this specification, the system refers to the entire apparatus including a plurality of apparatuses.

It should be noted that the effects described in the present specification are merely examples and are not limited, and may have other effects.

Note that the embodiments of the present technology are not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the present technology.

Note that the present technology may also be configured as below.
(1)
On the semiconductor substrate in order from the top surface of the substrate in the depth direction,
A first P-type impurity region,
A first N-type impurity region,
An image pickup device comprising: a second P-type impurity region and a second N-type impurity region, and a capacitance expanding portion forming a PN junction surface.
(2)
A read electrode for reading the accumulated charge is further provided on a surface of the first P-type impurity region facing the surface on which the second N-type impurity region is provided,
The image pickup device according to (1), wherein the capacitance expanding portion is formed in a region farther from the read electrode than the first N-type impurity region.
(3)
The image pickup device according to (1) or (2), wherein the second P-type impurity regions and the second N-type impurity regions are alternately arranged in the capacitance expanding section.
(4)
The semiconductor substrate is made of silicon,
The image sensor according to any one of (1) to (3), wherein the second P-type impurity region is formed of a material capable of filling an interface with the silicon with holes due to a work function difference.
(5)
The image pickup device according to any one of (1) to (4), wherein the first P-type impurity region and the second P-type impurity region are layers provided in different directions.
(6)
The image pickup device according to any one of (1) to (5), wherein the first N-type impurity region and the second N-type impurity region are layers provided in different directions.
(7)
The image pickup device according to any one of (1) to (6), wherein the first N-type impurity region is composed of a high-concentration N+-type impurity region and a low-concentration N−-type impurity region.
(8)
The image pickup device according to any one of (1) to (7), wherein the first N-type impurity region is a low-concentration N− region.
(9)
The image pickup device according to (2), in which a potential gradient is provided to read out the charges from the capacitance expanding section to the readout electrode.
(10)
The image pickup device according to any one of (1) to (9), wherein the second N-type impurity region in the capacitance expansion portion is formed in a quadrangular shape in a cross-sectional view from a predetermined direction.
(11)
The image pickup according to any one of (1) to (9), wherein the second P-type impurity region in the capacitance expanding portion is formed in a curved shape having a predetermined width in a cross-sectional view from a predetermined direction. element.
(12)
The image pickup according to any one of (1) to (9), wherein the second P-type impurity region in the capacitance expanding portion is formed in a circular shape having a predetermined width in a cross-sectional view from a predetermined direction. element.
(13)
The image sensor according to any one of (1) to (12), wherein the repeating interval between the second P-type impurity region and the second N-type impurity region of the capacitance expanding portion is 1 μm or less.
(14)
Floating diffusion is shared by multiple image sensors,
The image sensor according to any one of (1) to (13), wherein the readout electrode is arranged near the floating diffusion.

21 P+ region, 22 N+ region, 23 N- region, 24 P+ region, 300 image sensor, 301 N- region, 302 N+ region, 303 P+ region, 310 PN junction capacitance expansion part, 320 N-type impurity region, 330 P-type Impurity region, 500 image sensor, 501 N- region, 600 image sensor, 601 P+ applicable region, 610 PN junction capacitance expansion part

Claims (9)

On the semiconductor substrate in order from the top surface of the substrate in the depth direction,
A first P-type impurity region,
A first N-type impurity region,
A first low-concentration N-type impurity region having a concentration lower than that of the first N-type impurity region;
A capacitance expanding portion forming a PN junction surface from the second P-type impurity region and the second N-type impurity region ,
The first P-type impurity region, the first N-type impurity region, and the first low-concentration N-type impurity region are stacked in the first direction, and the second P-type impurity region and the second P-type impurity region are stacked. N-type impurity regions of are stacked in a second direction different from the first direction,
An image pickup device , wherein the concentrations of the first N-type impurity region and the second N-type impurity region are higher than those of the first low-concentration N-type impurity region . A read electrode for reading accumulated charge is further provided on a surface of the first P-type impurity region facing a surface on which the second N-type impurity region is provided,
The image pickup device according to claim 1, wherein the capacitance expanding portion is formed in a region farther from the read electrode than the first N-type impurity region. The image pickup device according to claim 1, wherein the second P-type impurity regions and the second N-type impurity regions are alternately arranged in the capacitance expanding section. The image pickup device according to claim 2, wherein a potential gradient is provided from the capacitance expanding section to the readout electrode in order to read out the charges. The image pickup device according to claim 1, wherein the second N-type impurity region in the capacitance expansion portion is formed in a quadrangular shape in a cross-sectional view from a predetermined direction. The image pickup device according to claim 1, wherein the second P-type impurity region in the capacitance expansion portion is formed in a curved shape having a predetermined width in a cross-sectional view from a predetermined direction. The image pickup device according to claim 1, wherein the second P-type impurity region in the capacitance expansion portion is formed in a circular shape having a predetermined width in a cross-sectional view from a predetermined direction. The image pickup device according to claim 1, wherein a repeating interval between the second P-type impurity region and the second N-type impurity region of the capacitance expanding portion is 1 μm or less. Floating diffusion is shared by multiple image sensors,
The image pickup device according to claim 2 , wherein the readout electrode is arranged in the vicinity of the floating diffusion.

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